Transferases are enzymes which are important in many biochemical systems. One of these, galactosyl transferase is involved in the lactose synthetase reaction which occurs in mammary and other tissues. This transferase and most other transferases cannot be directly followed by the usual arsenal of analytical probes. Despite their significance, these enzmyes are still awaiting the development of analytical techniques to study their role in biological systems. This proposal points out that the use of a piezoelectric crystal surface as a mass sensitive detector could overcome these current difficulties. The proposed analyzer, found within this proposal, should be sensitive, selective, inexpensive and easy to use. Once the galactosyl transferase system has been studied using this technique, other systems could also be studied, resulting in the development of a new analytical technique.